The invention relates to computer memories, and more particularly to non-volatile computer memories of the type which retain their stored data despite an interruption in power that supplies the memory, and still more particularly to non-volatile memories other than core memories.
Although in earlier years the dominant technology for mainframe memories was the ferrite core memory technology, for most applications lower cost, higher speed, lower power semiconductor memories have replaced the ferrite core memory technology. However, semiconductor memories have always suffered from one drawback compared to core memories in that semiconductor memories are generally volatile. That is, semiconductor memories (of the type that are presently practical for use in computer mainframe memories) lose stored data if the power supplying the computer is interrupted, even momentarily. Various techniques have been devised for overcoming this problem in most commercial computer systems, for example, by providing various battery back up systems. However, in some applications, especially in certain military applications, core memories remain the dominant technology, and the main reason for this is that non-volatility is needed. However, the continued development and refinement and lower costs of various semiconductor technologies would make it increasingly attractive to be able to utilize semiconductor memories in applications still dominated by the ferrite core technology, if there were a practical way of overcoming the volatility of semiconductor main memory technology.
Accordingly, it is clear that there remains an unmet need for a practical, inexpensive, non-volatile, high speed, lower power semiconductor memory replacement for certain ferrite core memory applications.